Email address list validate

email-address-list-validate · version 1.0.0 · Communications · free, no key needed

Check RFC 5322 address-list syntax, including dots, quotes, comments, and groups.

Use when you need to: validate an rfc 5322 address list · is this recipient list syntactically valid · reject consecutive dots in a mailbox domain.

Decide before calling

Read the versioned contract and the supported scope below. Reuse email-address-list-validate@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use email-address-list-validate@1.0.0 for validate an rfc 5322 address list. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• validate an rfc 5322 address list
• is this recipient list syntactically valid
• reject consecutive dots in a mailbox domain
• check group syntax in a recipient list
• find a bad local-part in an address list
• rfc 5322 address list syntax check

Not supported

• return the mailbox tree
• rewrite the address list into canonical form
• check that the domain has an MX record

Behavior

• Dot-atom-text is 1*atext *("." 1*atext) per RFC 5322 section 3.2.3, used by section 3.4.1. U+002E is not atext. A leading dot, a trailing dot, or two dots in a row is rejected in a local-part and in a domain, in both ascii and utf-8 modes. Inside a domain-literal or a quoted-string, a dot is ordinary text.
• mode ascii accepts only Unicode scalar values U+0000 through U+007F. mode utf-8 also treats U+0080 through U+10FFFF as atext, qtext, ctext, dtext and VCHAR, which is the RFC 6532 section 3.2 extension. The dot separator stays U+002E only.
• Well-typed text that is not a valid address-list returns valid false and a reason. Counts are zero in that case. Wrong types and limit breaches still throw.
• Obsolete null list slots and source routes (obs-route) are rejected. Domain-literals are not interpreted as IP addresses. RFC 5321 length limits and the SMTP requirement for a dot in the domain are not applied.
• The same text and mode always produce the same verdict. No clock, locale, or network.
• Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

Input

• text (string, required): max length 2048
• mode (one of "ascii", "utf-8", required)

Output

• valid (boolean, required)
• reason (one of "ok", "empty", "bad_local_part", "bad_domain", "invalid_address_list", "unbalanced_delimiter", "non_ascii", required)
• address_count (integer, required): min 0; max 32
• mailbox_count (integer, required): min 0; max 32
• group_count (integer, required): min 0; max 32

Limits

• max input bytes: 2048
• max addresses: 32
• max groups: 32
• max comment depth: 8
• max output bytes: 65536

Example

Request input:

{
  "text": "Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>",
  "mode": "ascii"
}

Response:

{
  "result": {
    "valid": true,
    "reason": "ok",
    "address_count": 3,
    "mailbox_count": 3,
    "group_count": 0
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "email-address-list-validate",
  "version": "1.0.0",
  "input": {
    "text": "Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>",
    "mode": "ascii"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/email-address-list-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"text":"Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>","mode":"ascii"}'

The machine-readable contract is at /v1/tools/email-address-list-validate/versions/1.0.0.

CLI

node cli.mjs run email-address-list-validate 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Email mailbox validate: Check one RFC 5322 mailbox for syntax only and return a stable reason code.
• Email address list deduplicate: Drop duplicate mailboxes in an RFC 5322 address-list, keeping the first one.
• Email address list parse: Parse an RFC 5322 address-list into ordered mailboxes, groups, and a canonical form.
• Email address list format: Format mailboxes and groups as one deterministic RFC 5322 address-list.
• Email mailbox parse: Parse one RFC 5322 mailbox into parts and canonical text, without a delivery claim.
• Email mailbox format: Render a canonical RFC 5322 mailbox from decoded parts, without a delivery claim.